“I have never given the matter a thought,” I said.

“There is a game of puzzles,” he resumed, “which is played upon a map.  One party playing requires another to find a given word — the name of town, river, state or empire — any word, in short, upon the motley and perplexed surface of the chart.  A novice in the game generally seeks to embarrass his opponents by giving them the most minutely lettered names; but the adept selects such words as stretch, in large characters, from one end of the chart to the other.  These, like the over-largely lettered signs and placards of the street, escape observation by dint of being excessively obvious; and here the physical oversight is precisely analogous with the moral inapprehension by which the intellect suffers to pass unnoticed those considerations which are too obtrusively and too palpably self-evident.  But this is a point, it appears, somewhat above or beneath the understanding of the Prefect.  He never once thought it probable, or possible, that the Minister had deposited the letter immediately beneath the nose of the whole world, by way of best preventing any portion of that world from perceiving it.

“But the more I reflected upon the daring, dashing, and discriminating ingenuity of D—­; upon the fact that the document must always have been at hand, if he intended to use it to good purpose; and upon the decisive evidence, obtained by the Prefect, that it was not hidden within the limits of that dignitary’s ordinary search — the more satisfied I became that, to conceal this letter, the Minister had resorted to the comprehensive and sagacious expedient of not attempting to conceal it at all.

“Full of these ideas, I prepared myself with a pair of green spectacles, and called one fine morning, quite by accident, at the Ministerial hotel.  I found D—­ at home, yawning, lounging, and dawdling, as usual, and pretending to be in the last extremity of ennui.  He is, perhaps, the most really energetic human being now alive — but that is only when nobody sees him.

“To be even with him, I complained of my weak eyes, and lamented the necessity of the spectacles, under cover of which I cautiously and thoroughly surveyed the whole apartment, while seemingly intent only upon the conversation of my host.

“I paid especial attention to a large writing-table near which he sat, and upon which lay confusedly, some miscellaneous letters and other papers, with one or two musical instruments and a few books.  Here, however, after a long and very deliberate scrutiny, I saw nothing to excite particular suspicion.